border-1px($color)
    position:relative
    &:after
        content:''
        display:block
        position:absolute
        left:0
        bottom:0
        width:100%
        border:1px solid $color
border-none()
    &:after
        display:none
bg-img($url)
    background-image: url($url+"@2x.png")
    @media(-webkit-min-device-pixel-ratio:3),(min-device-pixel-ratio:3)
        background-image: url($url+"@3x.png")
    